The present invention is directed generally to methods and apparatuses for dispensing adhesives on support media for microelectronic substrates. Packaged microelectronic substrate assemblies, such as memory chips and microprocessor chips, typically include a microelectronic substrate die mounted on a thin support substrate and encased in a plastic protective covering. The die includes functional devices or features, such as memory cells, processor circuits and interconnecting wiring. The die also typically includes bond pads or other terminal devices electrically coupled to the functional devices within the die. These terminals are connected to corresponding terminals of the support substrate with wire bonds, which are in turn electrically coupled to terminals accessible from outside the package to connect the die to buses, circuits and/or other microelectronic substrate assemblies.
In one conventional arrangement, a plurality of microelectronic substrates are attached to a single support substrate by dispensing dots of adhesive paste on the support substrate and pressing the microelectronic substrates against the dots. The adhesive paste is typically dispensed through one or more automatically actuated nozzles. Because the support substrate is generally thin and flexible, one conventional approach is to mount the support substrate on a flat vacuum table to keep the substrate level while the nozzles dispense the adhesive. The nozzles are then lowered into contact with the support substrate, then raised slightly to create a xe2x80x9cdispense gap.xe2x80x9d The adhesive is directed through the nozzles, across the dispense gap and onto the support substrate to form the adhesive dots. This process is repeated until the support substrate has the correct number of adhesive dots.
The amount of adhesive dispensed on the support substrate must be precisely controlled to ensure that the microelectronic substrates are adequately secured to the support substrate without using an excessive amount of adhesive. It is also desirable to prevent the adhesive from remaining in contact with the nozzle after being dispensed (which can cause the adhesive to attach to the nozzle instead of the support substrate). It is further desirable to prevent the adhesive from contacting exposed electrical terminals on either the support substrate or the microelectronic substrate.
One drawback with the dispense process described above is that it may not adequately control the amount of adhesive placed on the support substrate. For example, the vacuum table may not keep the support substrate flat enough, despite the vacuum force applied to the support substrate. As a result, a warped support substrate can be springy enough to remain biased against the nozzles as the nozzles move upwardly from the surface of the support substrate to form the dispense gap. This can locally reduce or eliminate the dispense gap. Accordingly, the support substrate can block the nozzles, and/or the adhesive can cling to the nozzles. In either case, the adhesive dispensed on the support substrate may be inadequate to secure at least some of the microelectronic substrates. When the adhesive bond between the microelectronic substrates and the support substrate are inadequate, some or all of the support substrate must be discarded, increasing the cost of producing packaged microelectronic assemblies.
The present invention is directed toward methods and apparatuses for dispensing a flowable adhesive on a support substrate that supports a microelectronic substrate. An apparatus in accordance with one aspect of the invention includes at least one dispense nozzle having at least one aperture configured to dispense the adhesive toward the support substrate, with the dispense nozzle being coupleable to a source of the adhesive. The apparatus can further include a standoff member operatively coupled to the at least one dispense nozzle. A contact surface of the standoff member projects beyond the aperture and is configured to contact the support substrate while the aperture of the dispense nozzle is spaced apart from the support substrate.
In one aspect of the invention, the apparatus can further include a carrier having a support surface configured to releasably carry the support substrate.
The carrier can include at least one forcing member operatively coupled to the support surface to force the support surface toward a selected position. The support surface can have a plurality of vacuum apertures configured to be coupled to a vacuum source to draw the support substrate toward the support surface. In still a further aspect of the invention, the nozzle can be one of a plurality of nozzles and the standoff member can be one of two standoff members. The standoff members can be spaced apart from each other by a distance sufficient to allow visual access to the nozzles.
The invention is also directed toward a method for dispensing a flowable adhesive on a support substrate for supporting microelectronic substrates. The method can include positioning a nozzle proximate to a support substrate, moving at least one of the nozzle and the support substrate relative to the other, and contacting a standoff member with the support substrate while the standoff member is operatively coupled to the nozzle and while an aperture of the nozzle is spaced apart from the support substrate to at least restrict further relative motion between the nozzle and the support substrate. The method can further include directing a flowable adhesive through the aperture of the nozzle and toward the support substrate while the standoff member contacts the support substrate.
In a further aspect of the invention, the method can include offsetting an aperture of the nozzle from the support substrate by a distance of from about 0.004 inch to about 0.005 inch while the standoff member contacts the support substrate. The method can further include directing the flowable adhesive through a plurality of nozzles, with at least one of the nozzles having a flow area different than that of another of the nozzles.